Step up transformer or upgrade phono preamp?

Maybe a dumb question, but let’s say I went with an SUT. I’ve noticed that some SUT’s do not specify how much gain is added, it only shows the coil winding ratio. Is this another way of telling me how much gain would be added to the chain? And if so how would you convert it? 

Question isn't the dumb one. It's another way to tell what you'll get.
Although you have to match 2 things per once - step up ratio and impedance. 

Let me guess what is going on here. In actual listening, you have no problem with gain. Isn’t that correct? But apparently you looked at some chart or read someone else’s opinion and decided that you must need more gain, that that must be the problem, even though you do not perceive a problem with gain. Whatever is the case, you cannot assess the need for more gain simply by looking at the gain of your MC phono section. You also need to know the additional gain added by your line stage or the high level section of your full function preamplifier. After that you also need to know the input sensitivity of your amplifier. All of these things affect your perception of gain and the sound pressure levels you will get from your speaker. Of course the efficiency of your speaker in converting watts of power into sound pressure is another factor determining the gain quotient of your system. Someone else can look at a chart or do a back of the envelope calculation and tell you that 60db is marginal gain for your cartridge, but by itself that doesn’t mean a thing. If you are happy with the sound pressure you are getting from your speakers, then you do not need more gain. Like Miller carbon said, perhaps you would be happier with a better sounding phono stage, not necessarily a higher gain phono stage or the addition of a SUT. A SUT is just a transformer. It adds to signal voltage while reducing signal current by a proportional fraction. The added gain is directly related to the turns ratio of the transformer. Any manufacturer will state that somewhere in the literature supplied with the transformer. But before you were to buy one, you would have to do more homework and decide what turns ratio is needed for your system. To do that you need to take into account the gain afforded by the moving magnet section of your phono stage, not the MC section. You can read about the use of a step up transformer on the Internet. There are many good sites for that. In my opinion, unless you really are lacking in gain, you really do not need a step up transformer in your system.

I have three MC phono setups:
MAGI Phonomenal phono pre + Live! MC-10 MC SUT
MAGI Phonomenal phono pre + Denon HA-1000
Allnic H1202

MAGI has two phono inputs.
MAGI + LIve! is just as good as Allnic.  Denon sounds a bit inferior to the other two.
If I were you, I would sell Vincent pho 701 and get Allnic.

I did a little homework, reluctantly.  Your phono stage provides 40db of gain in MM mode and 60db of gain in MC mode.  You would need to use the MM inputs with an external SUT. That means you would need a SUT with a turns ratio of 1:10, just to get a total of 60db of gain via your MM inputs, which you already have via your MC inputs. (A 10X voltage gain is equal to the 20db difference between the two phono sections.)  You would have to find a SUT with a higher turns ratio in order to benefit from any SUT in terms of gain.  Moreover, I see that your phono stage uses just one tube, the 12AU7, which means it must use solid state devices for gain and may even have a bult-in 1:10 SUT at its MC inputs.